Bottom Line:
Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments.The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses.

Background: The goal of total knee arthroplasty (TKA) is to restore knee kinematics. Knee prosthesis design plays a very important role in successful restoration. Here, kinematics models of normal and prosthetic knees were created and validated using previously published data.

Methods: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. The data from the three-dimensional models of the normal knee joint and a posterior-stabilized (PS) knee prosthesis were imported into finite element analysis software to create the final kinematic model of the TKA prosthesis, which was then validated by comparison with a previous study. The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.

Results: Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses. The PS knee prosthesis underwent an abnormal forward displacement compared with the normal knee and has insufficient, or insufficiently aggressive, "rollback" compared with the lateral femur of the normal knee. In addition, a certain degree of reverse rotation occurs during flexion of the PS knee prosthesis.

Conclusions: There were still several differences between the kinematics of the PS knee prosthesis and a normal knee, suggesting room for improving the design of the PS knee prosthesis. The abnormal kinematics during early flexion shows that the design of the articular surface played a vital role in improving the kinematics of the PS knee prosthesis.

Figure 3: The data comparison between the simulated model of normal knee and in vivo study.

Mentions:
Validation was performed to verify the accuracy of the target model by analyzing the trends of the output data and the values measured. There are two methods of validation: Experimental verification and literature comparison. Because it was difficult to find in vivo kinematics data, the method of literature comparison was used to validate the model in the present study. The displacements of the medial and lateral femur predicted by the normal knee model were compared with data from an in vivo study by Johal et al.[13] Because only the displacements of the medial and lateral femur were reported in Johal's study, we had to use the data for the model validation. The data comparison [Figure 3] between the simulated model of the normal knee and the results of the in vivo study shows that both the trends of the output data and the values measured, which were derived from the normal knee kinematics model, are very close to the results from Johal's in vivo study. Therefore, this model can be used for further analyses.

Figure 3: The data comparison between the simulated model of normal knee and in vivo study.

Mentions:
Validation was performed to verify the accuracy of the target model by analyzing the trends of the output data and the values measured. There are two methods of validation: Experimental verification and literature comparison. Because it was difficult to find in vivo kinematics data, the method of literature comparison was used to validate the model in the present study. The displacements of the medial and lateral femur predicted by the normal knee model were compared with data from an in vivo study by Johal et al.[13] Because only the displacements of the medial and lateral femur were reported in Johal's study, we had to use the data for the model validation. The data comparison [Figure 3] between the simulated model of the normal knee and the results of the in vivo study shows that both the trends of the output data and the values measured, which were derived from the normal knee kinematics model, are very close to the results from Johal's in vivo study. Therefore, this model can be used for further analyses.

Bottom Line:
Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments.The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses.

Background: The goal of total knee arthroplasty (TKA) is to restore knee kinematics. Knee prosthesis design plays a very important role in successful restoration. Here, kinematics models of normal and prosthetic knees were created and validated using previously published data.

Methods: Computed tomography and magnetic resonance imaging scans of a healthy, anticorrosive female cadaver were used to establish a model of the entire lower limbs, including the femur, tibia, patella, fibula, distal femur cartilage, and medial and lateral menisci, as well as the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments. The data from the three-dimensional models of the normal knee joint and a posterior-stabilized (PS) knee prosthesis were imported into finite element analysis software to create the final kinematic model of the TKA prosthesis, which was then validated by comparison with a previous study. The displacement of the medial/lateral femur and the internal rotation angle of the tibia were analyzed during 0-135° flexion.

Results: Both the output data trends and the measured values derived from the normal knee's kinematics model were very close to the results reported in a previous in vivo study, suggesting that this model can be used for further analyses. The PS knee prosthesis underwent an abnormal forward displacement compared with the normal knee and has insufficient, or insufficiently aggressive, "rollback" compared with the lateral femur of the normal knee. In addition, a certain degree of reverse rotation occurs during flexion of the PS knee prosthesis.

Conclusions: There were still several differences between the kinematics of the PS knee prosthesis and a normal knee, suggesting room for improving the design of the PS knee prosthesis. The abnormal kinematics during early flexion shows that the design of the articular surface played a vital role in improving the kinematics of the PS knee prosthesis.